weird cooling issues
The gaskets are 3 layer MLS and look the same as the BTRs, michigan motorsports, OEM LS1 5.7 GM gaskets... They might not be made in Germany or mexico but I agree they could be of "lesser" quality. That is the reason I copper coated them just to be safe. I have three 5.3LS motors, one uses stock GM LS1 gaskets from GM performance (same 3 layer) with no coating and ARP head bolts. This engine has seen 16psi and I drive it all the time over the last 10 years. The other 5.3 has the same cheap Chinese head gaskets and ran fine with no coating/spray but uses speedmaster head studs. This motor used the same head gasket no coating and speedmaster head studs and took 2 years before it started leaking. This is why I copper coated them. My thoughts are that most of the gasket manufactures are sourced from the same place and just relabeled (BTR, Michigan motorsports etc) I'm sure felpro, GM and cometic are unique in sourcing and manufacturing but I've seen some issues with the felpros not having the correct hold orientation and the Cometics are SUPER picky about prep and flatness. I couldnt see paying a premium for the same 3 layer gaskets or even a 5 or 7 layer LS9. This is a low boost 5.3 which wouldn't have even sweat with stock 150k gaskets... no need for LS9 or special gaskets. Their is nothing special about MLS head gaskets (just layers of steel shims) and if you can reuse a stock set with just copper spray I have high confidence that this will solve my problem.
Not sure if you saw/read here but I used these gaskets (installed on the engine but never run) and then had to pull the heads due to a rust issue and then reinstalled without any copper coat. These gaskets were essentially used and then reused so I can't blame the gaskets honestly. I should have replaced them or sprayed them but I've never sprayed head gaskets before. So that is on me but new gaskets with spray I'm very confident that this should be fixed.
I'm not running bolts, Speedmaster head studs which were torqued to 65ftlbs which is within the working limits of the studs... people who go over 70ftlbs push them too hard to be reused.
Last edited by customblackbird; Oct 14, 2025 at 10:34 AM.
A DeWitts radiator w/A4 connections, a 25% UD balancer, 160° stat, and an Edelbrock 8896 mechanical H2O pump. A few years back, I was ready to pull both heads, as it would lose enough coolant over the summer to go from the full mark to just below the lower level mark. No drips under the car. Freeway temps would go from 180° to 174°, then back again!! Always ran 178°-180° on freeway regardless of ambient. As I was looking at what to remove first to pull the heads, I saw a drip from a heater hose. It immediately evaporated. Then another drip in 15-20 seconds. The engine had heat sunk, increasing the pressure slightly until it dropped enough to stop. The cause? The factory sprung hose clamps had lost a tiny bit of tension. This happened several years ago, at least 4 years back. Installed a traditional hose clamp, and it has never leaked again. Saved me from buying $160 worth of head gaskets, and a Helluva lot of work!!! FWIW.....
Last edited by customblackbird; Oct 14, 2025 at 10:35 AM.
i also ended up getting Jays Tstat block off and installed it. I would say it warms up a bit slower just idling. I’m hoping to take the car out today for a quick trip and confirm the engine temps and that I don’t get anything in the expansion tank like oil froth.
Fun fact I've driven the car when it was 40F out and I saw once saw 178F cruising lol. In this current 55F air my fan never comes on.
Pooter, I had only one previous turbo combo, had a looped hose. It was 21 years ago. I ran stock f-body fans which are pretty robust. Turbo cooling/cruising knowledge has gotten better over the years, my tuner Jon Capizzi has told me on a few occasions that turbo combos burn lazy so the move is to increase cruise and idle timing a noticeable amount over an NA combo.
My looped hose old NA and Nitrous builds ran fine cooling wise, the turbo changes things.
Overflow cap, looks not as "oily" like it was previously in this thread.
This is looking in the overflow tank (not the radiator)
Radiator
tester after 10 min or so idling and light throttle blips.
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